Lymphocytic Interstitial Pneumonitis



Lymphocytic Interstitial Pneumonitis


Jud W. Gurney, MD, FACR





Key Facts


Terminology



  • Lymphoproliferative disorder ranging from follicular bronchiolitis to low-grade lymphoma



    • Diffuse disease commonly referred to as LIP


    • Focal disease commonly referred to as pseudolymphoma


Imaging Findings



  • Radiographic findings centered on lymphatic pathways in lung



    • Ground-glass opacities


    • Centrilobular nodules, poorly defined


    • Thin-walled cysts, perivascular, 1-30 mm in diameter, do not resolve


  • Centrilobular nodules may evolve into cysts


Top Differential Diagnoses



  • Nonspecific Interstitial Pneumonitis


  • Hypersensitivity Pneumonitis


Pathology



  • Chronic antigenic stimulus elicits lymphoproliferative response, may be



    • Idiopathic (rare)


    • Autoimmune: Sjögren syndrome


    • Viral infection: HIV (especially in children)


    • Castleman disease


  • Diffuse infiltration of alveolar septa by lymphocytic infiltrate


Clinical Issues



  • Nonspecific cough, dyspnea


  • Dysproteinemia (75%)


  • May evolve into B-cell lymphoma, especially in Sjögren (5%)







Coronal NECT shows multiple thin-walled cysts image in a background of diffuse ground-glass opacities. The diagnosis was lymphocytic interstitial pneumonitis.






Axial CECT shows peribronchovascular ground-glass opacities image in a patient with Sjögren syndrome and lymphocytic interstitial pneumonitis.


TERMINOLOGY


Abbreviations and Synonyms



  • Lymphocytic interstitial pneumonia (LIP), pseudolymphoma, lymphoid interstitial pneumonia, diffuse hyperplasia of bronchus-associated lymphoid tissue (BALT), mucosa-associated lymphoid tissue (MALT)


Definitions



  • Part of spectrum of idiopathic interstitial pneumonias



    • Lymphoproliferative disorder ranging from follicular bronchiolitis to low-grade lymphoma


  • Diffuse disease commonly referred to as LIP


  • Focal disease commonly referred to as nodular lymphomatoid hyperplasia (pseudolymphoma)


  • Nonneoplastic lymphoproliferation must be differentiated from lymphoma by immunologic stains



    • Monoclonal cell lines in lymphoma, polyclonal in nonneoplastic lymphoproliferative disorders


IMAGING FINDINGS


General Features



  • Best diagnostic clue: Thin-walled cysts and centrilobular nodules


  • Patient position/location: Centered on lymphatic pathways: Peribronchovascular, centrilobular, septa, and pleura


CT Findings



  • Radiographic findings centered on lymphatic pathways in lung



    • Peribronchovascular, septa, pleura


  • Diffuse (LIP)



    • Ground-glass opacities (100%)



      • Distribution: Bilateral (90%), diffuse (60%), peripheral distribution (10%)


    • Centrilobular nodules



      • Poorly defined, 2-4 mm in size


    • Thin-walled cysts



      • Most distinctive finding (80%)


      • Range 1-30 mm in diameter (average 5 mm)


      • Involve < 10% of total lung


      • May be isolated finding



    • Combination of ground-glass opacities, centrilobular nodules, and thin-walled cysts common


    • Other findings (related to lymphatic pathways)



      • Subpleural nodules (> 50%)


      • Septal thickening (80%)


      • Thickening of small bronchovascular bundles (tree-in-bud pattern)


      • Bronchiectasis (20%)


      • Rarely fibrosis and honeycombing


  • Focal (pseudolymphoma)



    • Air-space mass, consolidation with air-bronchograms


    • Nodules (> 5 mm)



      • Peribronchial in distribution


      • Up to 30 mm in size (average 10 mm)


    • No lobar predilection


    • Cavitation rare


  • Evolution



    • All findings may resolve except for cysts


    • Centrilobular nodules may evolve into cysts


    • Airspace consolidation may evolve into honeycombing


  • Lymph nodes may be enlarged (up to 70%), usually multiple nodal groups



    • More common in AIDS patients


    • Not large enough to see on radiography


  • Pleural effusions rare


Radiographic Findings



  • Usually nonspecific findings, better evaluated with CT



    • Diffuse disease (LIP)



      • Diffuse interstitial thickening, predominately basilar


      • Multiple pulmonary nodular opacities often with air-bronchograms (more common in AIDS)


    • Focal



      • Focal central airspace mass(s), segmental or lobar in size mimicking pneumonia


      • Over time gradually grow toward periphery of lung


      • May also arise in lung periphery


      • Unilateral or bilateral


  • Pleural effusions rare


  • Associated findings



    • Anterior mediastinal mass: Thymoma



      • Predisposing condition for hypogammaglobulinemia or myasthenia gravis, either of which may lead to LIP


    • Splenomegaly


DIFFERENTIAL DIAGNOSIS


Nonspecific Interstitial Pneumonitis



  • Cellular or fibrotic, temporally homogeneous at histology


  • Idiopathic or seen with collagen vascular diseases


  • Ground-glass opacities in bronchovascular distribution


Angioimmunoblastic Lymphadenopathy



  • Lymphoproliferative disorder associated with dysproteinemia and immunodeficiency


  • Generalized lymphadenopathy and hepatosplenomegaly


  • Skin rash


  • Pleural effusion


  • Lung may be normal or have focal mass-like areas of consolidation


Castleman Disease



  • Benign lymphoproliferative hyperplasia of lymph nodes


  • Hilar or mediastinal adenopathy



    • Hyaline vascular form: Nodes have intense contrast enhancement


  • Lungs less likely to be abnormal (if abnormal may be due to co-existing LIP)


Lymphomatoid Granulomatosis



  • Multiple pulmonary nodules (may be cavitary)


  • Skin rash


  • Central nervous system (CNS) disease


Hypersensitivity Pneumonitis



  • Appropriate antigen exposure



  • Diffuse ground-glass opacities and centrilobular nodules


  • Lobular air-trapping more common


  • Cysts and adenopathy much less common


Thin-Walled Cysts



  • Laryngotracheal papillomatosis


  • Pneumatoceles



    • Trauma


    • Pneumocystis jiroveci pneumonia


    • Staphylococcus pneumonia


    • Hydrocarbon ingestion


  • Langerhans granulomatosis


  • Lymphangiomatosis


  • Centrilobular emphysema


  • Metastases


  • Birt-Hogg-Dubé syndrome: Multiple renal oncocytomas/cancer, skin lesions


PATHOLOGY


General Features

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Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Lymphocytic Interstitial Pneumonitis

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